1. Field of the Invention
The invention relates to a method of manufacturing a metal strip in which the metal strip is guided over a number of rolls under such strip tension and is advanced in a transporting direction so that it is flat to a large extent at least between two rolls. The invention further relates to an apparatus for manufacturing a metal strip.
2. Description of the Prior Art
During rolling and skinpass rolling of a metal strip, the flatness, together with the thickness and cleanliness of the strip, is a decisive factor. Therefore, it is necessary to undertake inspection during manufacturing of a metal strip to insure quality of the production, wherein, if necessary, based on the results produced by inspection, the manufacturing process should be modified.
To the end, in conclusion of a rolling process, often, the metal strip is subjected to the flatness measurement, wherein unevenesses of the strip should be revealed. To this end, flatness measuring rollers are used which are pressed with a predetermined prestress against a metal strip that is guided under tension. By measuring the imprints of the flatness measuring roller resulting from the unevenesses of the metal strip, a conclusion can be made about the unevenesses in the metal strip. Also known are systems that visualize differences in tension caused by its variations.
Unevenesses in a metal strip can be determined not only with contacting rollers but also in contactless manner. To this end, e.g., the JP 2000046752 A discloses an optical system that has an illuminating device for the strip and cameras. Therefore, it is possible to three-dimensionally measure the surface of a metal strip and determined the measurement result.
Flatness of a metal strip can also be measured with an apparatus such as disclosed in EP 1 418 400 A2. Here, likewise, deviations are determined with a camera (CCD-Kamera: Charge-Coupled-device camera).
Similar systems are disclosed in DE 197 58 466 A1 and DE 199 32 324 A1.
In all of the above-mentioned cases, unevenesses of the strip surface are measured and, if necessary, change of process parameters is undertaken.
It has been determined that specific measurement results under a corresponding strip tension are difficult to interpret because, dependent on the strip tension that is applied to the metal strip, flatness changes. Therefore, based on the strip tension to which a rolling stock is subjected in a rolling process, the stress differences over the strip width in form of buckling or unevenesses cannot be recognized or are recognizable with much difficulty.
It is particularly desirable to be able to visualize the stress distribution over the width of the metal strip in order to make a conclusion about the strip quality. At that, the apparatus for this determination should be formed in a space-saving manner and should not require any large expenses for its installation and operation.